Conventionally, there is a technology of forming high-precision plastic products formed of plural miniaturized components by way of molding. More specifically, there is a technology of forming: (1) miniature lens arrays; and (2) minute optical fiber arrays.
(1) Conventional Technology Related to Miniature Lens Arrays
For the conventional technology related to miniature lens arrays or microlens arrays, Japanese Laid-Open Patent Application 1-107202 (Patent Reference 1), Japanese Laid-Open Patent Application 2004-341474 (Patent Reference 2); Japanese Laid-Open Patent Application 2004-45586 (Patent Reference 3) are cited.
More specifically, Patent Reference 1 discloses a manufacturing method of a lens array according to the steps of: arraying GRIN (graded index) cylindrical lenses in a mold such that the optical axes thereof are aligned in a predetermined direction; and injecting a molten resin into the mold to form a molding in which the lens array and the resin are integrated.
Further, Patent Reference 2 describes the method for producing an optical component by an extrusion molding process. More specifically, the technology of Patent Reference 2 aims for a production method of an optical component characterized by long lifetime of the mold, capability of forming the lenses without distortion or optical defects and capability of integrating the lenses easily into a main apparatus with high precision.
Thus, a lens holding member is placed on a lower mold in such a manner that the lens holding member is formed with a large number of lens holes, and lenses are placed on the respective lens holes of the lens holding member. Thereby, the lower mold and the upper mold are formed respectively with a lower lens mold surface and an upper lens mold surface with the diameter smaller than the diameter of the lens holes, and lenses are formed by pressing the lower mold and the upper mold with each other. By using different materials for the lens and the lens holding member, it becomes possible to suppress optical noise of the lens. Particularly, by using a metal for the lens holding member, it becomes possible to mount the lens array to a main apparatus easily by way of soldering.
Further, Patent Reference 4 provides the method of manufacturing a high-precision composite molding having a thin optical shielding part. The reference eliminates the problem of misalignment between a molded product and a molding apparatus applying a secondary molding process to the molded product and enables manufacturing of a composite by molding process with high precision in terms of dimensions and pattern transfer precision. With this prior art, reference positions are defined respectively to the molded product produced by the first molding process and to the mold used for the secondary molding process for mutual alignment at the time of initial setup of the secondary molding process. Further, adjustment of dimensions is achieved by way of expanding or shrinking the primary molding or the mold or by way of mechanical dimensional adjustment. Further, the start timing of holding the primary molding in the secondary molding apparatus is controlled by detecting the mutual positional relationship therebetween or by evaluating the mutual positional relationship based on the linear thermal expansion coefficients by detecting the temperature. Alternatively, the start timing may be controlled based on the time calculated from the temperature and the dimension. Thereby, the start timing of the secondary molding is defined as the timing in which the temperature of the primary molding has reached a temperature higher than the glass transition point by 3-25° C.
Japanese Patent 3,521,469 (Patent Reference 5) describes a manufacturing method of resin lens array according to the process steps of: forming a resin layer on one side of a flat substrate by applying a transparent resin with a uniform thickness; urging the resin layer against an optical shielding plate of an optically shielding material formed with plural through-holes; forming lenses by extruding a part of the resin layer into the through-holes of the optical shielding plate; curing the resin layer to form a lens array sheet; and fixing the substrate and the optical shielding plate by way of the resin layer.
Further, Japanese Laid-Open Patent Application 2004-45586 provides a method of manufacturing a microlens array sheet having an optical shielding layer comprising the steps of: irradiating a ultraviolet radiation to a microlens array sheet comprising a consecutive lamination of: a transparent support substrate carrying microlenses at one side and a transparent a photosensitive layer or a thermoplastic resin layer at the other side; a UV-cure adhesive resin layer colored in black; and a protective film layer, such that the ultraviolet radiation is applied to the side where the lenses are formed; curing the UV-cure resin layer at the parts where the UV radiation is focused by the microlenses to cause transfer of the cured resin layer corresponding to the focused parts to the protective film layer; peeling off the cured resin layer of the focused parts from the transparent photosensitive layer or the thermoplastic layer by peeling the protective film layer therefrom and forming an optical shielding pattern of the UV-cure resin layer in correspondence to the parts not exposed to the UV radiation and remaining in intimate contact with the transparent photosensitive layer.
(2) Conventional Technology Related to Optical Fiber Arrays
There are various conventional arts related to manufacture of optical fiber arrays.
Japanese Laid-Open Patent Application 2004-118119 (Patent Reference 6) discloses a technology related to plastic optical fiber arrays and manufacturing method thereof. This prior art technology enables manufacturing of optical fiber array characterized by smooth core surface and reduced optical transmission loss with low cost in short time while using a simple manufacturing apparatus, and comprises the steps of: lowering a comb-shaped molding that includes plural bar-shaped fingers extending parallel with each other toward a UV-cure molten resin of liquid state such that end parts of the bar-shaped fingers contact with the molten resin simultaneously; pulling up the bar-shaped fingers; curing the resin pulled up from the molten resin with the foregoing end parts to form plural core parts simultaneously; forming a cladding layer by dipping the entire core parts into a molten UV-cure resin (cladding resin solution) to form a cladding layer composite; placing the cladding layer composite thus formed into a vessel together with a molten thermoplastic resin of low viscosity; forming the entire thermoplastic resin by heating the vessel together with the molten resin and the cladding layer composite to form a protective part; cutting the molding thus formed including therein the comb-shaped part at the end parts of the bar-shaped fingers; and polishing the cross-section of the end parts thus formed.
Japanese Laid-Open Patent Application 8-112873 (Patent Reference 7) discloses the technology related to a porous body and manufacturing process thereof.
More specifically, this reference aims for a light weight porous body of excellent thermal insulation and compressive strength and provides a sheet-shaped porous body comprising: square-shaped cells forming a lattice pattern in a thermoplastic resin body; and a highly expandable thermoplastic resin composition formed in each cell, the highly expandable thermoplastic resin composition having an expansion ratio of 20 times as large as the thermoplastic resin forming the cells.
Further, Japanese Laid-Open Patent Application 10-80964 (Patent Reference 8) discloses a honeycomb structure and manufacturing technology thereof.
More specifically, the reference teaches a strong transparent honeycomb structure of stable quality over a long period of time and the manufacturing method thereof, wherein the honeycomb structure includes three-dimensional packing of columnar cells of polygonal cross-sectional shape in a resin with high density. Thereby, the cells are formed without providing a junction part between the cell walls, and the cells are formed by placing an expandable substance in a resin with a three-dimensionally regular arrangement and by inducing expansion of the expandable substance.    Patent Reference 1 Japanese Laid-Open Patent Application 1-107202 official gazette    Patent Reference 2 Japanese Laid-Open Patent Application 2004-341474 official gazette    Patent Reference 3 Japanese Laid-Open Patent Application 2004-45586 official gazette    Patent Reference 4 Japanese Laid Open Patent Application 2003-80543 official gazette    Patent Reference 5 Japanese Patent 3,521,469    Patent Reference 6 Japanese Laid-Open Patent Application 2004-118119 official gazette    Patent Reference 7 Japanese Laid-Open Patent Application 8-112873 official gazette    Patent Reference 8 Japanese Laid-Open Patent Application 10-80964 official gazette    Patent Reference 9 Japanese Patent Publication 56-34780 official gazette